Pumping apparatus



Sept. 1, 1964 L. TYREE, JR 3,1

PUMPING APPARATUS Filed March'6, 1963 2 Sheets-Sheet 2 firm 12101" 161403 5/66; k/l' United States Patent 3,146,717 PUMIING APPARATUS LewisTyree, In, 9955 S. Hamilton Ave., Chicago, Ill. Filed Mar. 6, 1963, Ser.No. 263,260 4 Claims. (til. 103-5) This invention relates to apparatusfor pumping cryogenic liquids and more particularly to rotary positivedisplacement pumps for pumping such liquids.

The handling of cryogenic liquids (e.g. oxygen, nitrogen, etc.) having aboiling point which is lower than ambient temperature has presented avariety of difiiculties which have heretofore not been completelyresolved. One prime example of a situation wherein such difficulties areincurred is the pumping of a cryogenic liquid from a low pressurecontainer to a high pressure storage tank or pipe line. This is truesince the cryogenic liquids, which are usually and most desirablyhandled in a nearly natural boiling condition, are normally absorbingheat from the surrounding environment before and during pumping, andheat is absorbed by the liquid as work is being done by the pump. Whenso heated cryogenic liquids tend to first come to their boiling pointand then undergo a phase transition to a gas or vapor state (i.e.fiash). Not only is this flashing undesirable since it leads to vaporlocking or failure of the pumping system but it also prevents theaccurate metering of the liquid being delivered to the high pressurestorage tank. Attempts to resolve this heat absorbing difiiculty and topreclude flashing which results therefrom have centered about the use ofauxiliary refrigerating or sub-cooling means that substantiallyincreases the cost or complexity of the pumping system.

It is the prime object of the present invention to provide an improvedapparatus for pumping cryogenic liquids.

A further object of the present invention is to provide a rotarypositive displacement pumping apparatus for handling cryogenic liquidswhile minimizing the possibility of vapor lock.

A further object of the present invention is to provide an essentiallyvapor lock-free rotary positive displacement pump for handling cryogenicfluids which does not require auxiliary refrigerating or sub-coolingmeans.

Still another object of the present invention resides in the provisionof an improved rotary positive displacement pump of cryogenic liquidswhich is relatively simple and inexpensive both in construction andoperation.

Other objects and advantages of the present invention become apparentfrom the following detailed description when considered in conjunctionwith the accompanying drawings wherein:

FIGURE 1 is a cross sectional view illustrating a preferred embodimentof the pumping apparatus of the present invention;

FIGURE 2 is a cross sectional view taken generally along the line 2-2 inFIGURE 1;

FIGURE 3 is a cross sectional view taken generally along the line 33 inFIGURE 1; and

FIGURE 4 is a cross sectional view of the pumping apparatus takengenerally along the line 44 in FIG- URE 1.

In general, the present invention provides improved rotary positivedisplacement pumps {c.g. gear type, lobe type, vane type, etc.) forhandling cryogenic liquids. In a preferred embodiment of the invention,a sealed housing is provided that defines an intake chamber, a pumpingchamber, a passageway providing communication between the chambers, andintake and outlet ports communicating with the intake and pumpingchambers, respectively. A first rotary positive displacement pumping3,146,717 Patented Sept. 1, 1964 means is provided in the intake chamberso that successive portions of cryogenic liquid available at the intakeport are delivered to and through the passageway to the pumping chamberby successively generated delivery compartments defined by this firstrotary pumping means. A second rotary positive displacement pumpingmeans is provided within the pumping chamber. Rotary motion imparted tothe second rotary pumping means results in pumping and the continuousmetered discharge of liquid from successively generated pumpingcompartments defined by the second rotary pumping means.

The structural arrangement of the pumping components is such that thefirst rotary positive displacement pumping means within the intakechamber does not perform any substantial amount of work but ratherserves to deliver successive quantities of the cryogenic fluid from theintake port to the mouth of the passageway leading to the pumpingchamber. Moreover, the second rotary positive displacement pumping meansof the pump ing stage is proportioned in relation to the pumping meansofthe intake stage so that a degree of controlled cavitation (flashing) isrealized as the fluid is continuously delivered from the intake chamberthrough the communicating passageway to the pumping chamber.

That is, each of the successively generated pumping compartments of thepumping stage has a greater volumetric capacity than do thecorresponding and successively generated delivery compartments of theintake stage that supply liquid to the pumping compartment. The amountof the resulting cavitation (flashing) is controlled so that theindividual and successively generated pumping compartments, whencommunicating with the corresponding delivery compartments, each receivesome vapor and some liquid. This condition is necessarily maintainedsothat the possibility of surging cavitation is eliminated (i.e. theintermittent delivery of pure vapor followed by pure liquid, etc.). Themost certain means to assure this controlled cavitation results fromproportioning the communicating passageway including the regionsadjacent the inlet and outlet thereof with a volumetric capacity suchthat some liquid must pass into each successively generated pumpingcompartment of the second stage. That is, the volumetric capacity ofthis fluid conduit or passageway is selected so that it is preferablyless than the volume of liquid delivered to it by the deliverycompartments of the intake stage during the interval of time that onegenerated pumping compartment is positioned to receive liquid. However,it should be understood that in some applications the volumetriccapacity of the communicating passageway might be equal to or slightlygreater than the volume of the delivered liquid. The important factor isthat some liquid be delivered into each successively generated pumpingcompartment of the second stage.

The manner in which rotary positive displacement pumps in accordancewith the present invention achieve the eflicient pumping of cryogenicfluids, absent vapor lock and without the need for auxiliary sub-coolingmeans, will be fully appreciated from a detailed consideration of thepreferred embodiment illustrated in FIGURES l- 4. Although the presentinvention contemplates any of the various forms of rotary positivedisplacement pumps, the embodiment illustrated in the drawings andspecifically described herein is a rotary gear type pump. Moreover,various structural details that would be obvious to one skilled in theart, that are subject to variation in different types of rotary pumpconstructions, and that do not form a part of the invention are notdescribed in detail.

Referring in particular to the drawings, FIGURE 1 illustrates a rotarygear type positive displacement pump that includes an outer housing 10.The major portion of the housing is formed by a pair of suitablyproportioned outer casings 11 and 12 that are preferably formed of amaterial such as bronze or austenitic stainless steel. The casings 11and 12 are mounted in sealing relationship on opposite sides of acentral plate 13 by a plurality of suitable fasteners 14. The plate 13is also preferably formed of bronze or austenitic stainless steel.

As shown, the upper casing 11 is provided with an intake port 16 thatcommunicates with an intake chamber 17 which is defined by the casing 11and the mating central plate 13. The intake chamber 17 serves as thehousing for a pair of externally contacting spur gears 18, which arealso preferably formed of a material such as bronze or austeniticstainless steel. More particularly, the intake chamber 17 formed in thecasing 11 includes a pair of overlapping cylindrical chamber sections 19(FIGURE 3), which are proportioned to receive the gears 18 in matingrelationship while at the same time allowing the free and unrestrictedrotation thereof as hereinafter described.

Similarly, the outer casing 12 in conjunction with the plate 13 definesa pumping chamber 21 which is comprised of a pair of overlappingcylindrical chamber sections 22. A pair of heliquad gears 23 are mountedfor rotation within the chamber 21 in a manner similar to the mountingof the gears 18 within the chamber 17. As shown in FIGURE 2 the pumpingchamber 21 communicates directly with an outlet port 25. The outercasings 11 and 12 are further provided with outwardly projectinggenerally cylindrical bearing housings 26 and 27, respectively. Theseoutwardly projecting housings are preferably closed and sealed by endplates 28 and 29 so as to define enclosed housings for conventionalself-lubricating bearing members 30 formed of materials such aspolytetrafluoroethylene or polychlorotrifiuoroethylene that are soldunder the trademarks Teflon and Kel-F, respectively. The bearing members30 are proportioned to receive the ends of shafts 31 and 32 whereon thegears 18 and 23 are mounted.

More particularly, the shaft 31 which is preferably driven by aconventional drive motor (not shown) extends into the housing 10 througha suitable packing structure 33 provided in the apertured portion of oneof the end plates 28. As shown, this driven shaft has one of the coaxialspur gears 18 and one of the heliquad gears 23 keyed thereto (FIGURES 3and 4) by keying members 34 and has the free end thereof positionedwithin a bearing member 30. The central portion of the shaft 31 confinedwithin the housing extends through another self-lubricating bearing andsealing member 35 provided in an apertured portion of the central plate13.

With the driven shaft so mounted, rotary motion imparted thereto resultsin the free and unrestricted rotation thereof thereby causing the gears18 and 23 secured thereto to be similarly driven. The other of the gears18, which is mounted on the shaft 32 and mates with the driven gear 18,is driven and caused to rotate thereby. Accordingly, the other of thegears 23, which is also keyed to the shaft 32, has rotary motionimparted thereto.

In this connection, the shaft 32 has the other of the gears 18 and 23keyed thereto by keying members 34 and is suitably mounted for rotationwithin the end bearing members 30 and a central bearing and sealingmember 35. The mounting of the shaft 32 and the gears secured theretois, in a conventional manner, effected so that the gears 18 of theintake stage are maintained in close meshing relationship and actuallycontact so that rotary motion imparted to one of the gears causes theother to be similarly driven. Although the teeth of the driven heliquadgears 23 do not actually contact, these gears are mounted so that theclearance volume between the teeth thereof is minimized to precludeleakage. Moreover, the entire mounting of the gears, shafts and bearingmembers is such that 4, any void spaces within the chambers whereincryogenic liquid might accumulate are substantially eliminated.

More particularly, the arrangement of the gears 18 and 23 and themounting thereof within the chamber sections 19 and 22, respectively, issuch that the free rotation of the gears is insured although theperipheral, upper and lower surfaces of each are closely fitted adjacentthe chamber defining walls of the outer casings 11 and 12 and thecentral plate 13. Accordingly, during the rotation of the gears withinthe intake and pumping chambers, leakage between adjacent chambers andbetween successively generated delivery compartments 18a or pumpingcompartments 23a is essentially precluded.

As best seen in FIGURE 2, the central plate 13 is provided with adiagonally communicating passageway 35 that serves to link the intakechamber 17 to the pumping chamber 21. Accordingly, liquid delivered tothe region in the intake chamber adjacent the mouth of the passageway 36is delivered therethrough to the region in the pumping chamber adjacentthe discharge end of the passageway. More particularly, successiveportions of the liquid supplied at the inlet port 16 are delivered intoand confined within the successively generated delivery coinpartments180. As the gears 13 are rotated in the direction of the arrows inFIGURE 3, these confined portions of the liquid are successivelydelivered to the region de fined by the intake chamber defining surfaceof the central plate 13 and the peripheral portions of the gears 18.Thereafter, the fluid is circulated into and through the communicatingpassageway 36 and delivered to the region at the oulet of the passagewaydefined by the oppositely disposed pumping chamber defining surface ofthe plate 13 and the peripheral portions of the heliquad gears 23.

The relative size and fitting of the gears 18 and 23 and the dimensionsof the passageway 36 are such that during the period that the individualpumping compartments 23a defined by the heliquad gears are positioned toreceive liquid from the intake chamber some liquid and some vapor willbe delivered thereto. This results from the interrelated structural andvolumetric characteristics of the pump generally outline above.

More particularly, the heliquad gears 23 of the pumping stage, which arepreferably formed of bronze or austenitic stainless steel, havedimensions such that volumetric capacity of the individual pumpingcompartments 23a generated during the rotation thereof is greater thanthat of the corresponding delivery compartments 18a generated within theintake stage as a result of the rotation of the mating gears 18.Accordingly, an amount of vaporization (i.e. flashing) occurs as thefluid expands into the individual pumping compartments 23a from thecorresponding delivery compartments 13a.

By controlling this volumetric capacity differential between thedelivery compartments 18a and the pumping compartments 23a, the degreeof flashing can also be controlled so that some liquid and some vapor iscontinuously discharged into the communicating passageway.

In addition, the communicating passageway including the regions adjacentthe inlet and outlet ends of the passageway is dimensioned so that aportion of the liquid delivered thereto during any selected intervalwhen a single pumping compartment 23a is positioned to receive fluid isnecessarily transferred to this pumping compartment. Consequently, eachof the successively generated pumping compartments are continuously andassuredly supplied with some liquid that is conveyed to the outlet port25, compressed and discharged to the high pressure portion of thesystem. This conveyance is carried out as the heliquad gears 23 aredriven in the direction of the arrows in FIGURE 4. As previously pointedout, the transfer of some liquid to each pumping compartment 23a ispreferably assured by forming the passageway 36 with a volumetriccapacity less than the volume of liquid that might be delivered theretowhen a pumping compartment is positioned to receive the liquid. However,a passageway having a volumetric capacity equal to or slightly greaterthan the volume of liquid that might oe delivered may be employed insome applications.

The novel structural configuration of the pump, as described above,leads to essentially vapor lock free operation and yields relativelyefficient pumping of cryogenic liquids. Moreover, the gears 18 of theintake stage act essentially as delivery members and perform a minimalamount of work inasmuch as the liquid delivered thereby from the inletport to the communicating passageway is essentially passing from ahigher pressure to a lower pressure region. This advantage, which stemsfrom the volumetric capacity differential between the generated deliverycompartments 1811 and pumping compartments 23a that are suppliedthereby, necessarily results in less heat input to the liquid as it istransferred from the inlet port to the communicating passageway 36.

Moreover, flashing of the liquid occurs as the delivery compartments 18adischarge their contents at the inlet to the communicating passageway 36and the decrease in temperature accompanying this flashing results insome cooling of the gears 18. Accordingly, the possibility ofvaporization of the incoming liquid at the inlet port as a result ofheating is eliminated. An additional advantage of the pump construction,as described above, stems from the larger volumetric capacity of thegenerated pumping compartments 23a. That is, the amount of leakage thatoccurs per volume of liquid pumped by each of these generated pumpingcompartments is reduced. Accordingly, heat pickup, which is incidentalto the friction created by the leakage of fluid from the generatedpumping compartments 23a around the peripheral and end sections of theheliquad gear teeth, is minimized.

One specific embodiment of a gear type pump embodying the structuralfeatures as previously described has a pumping capacity of 3 gallons aminute when transporting oxygen at a temperature of 292 F. from an inletport having a pressure of 5 p.s.i.g. to an outlet port hav-' ing apressure of 500 p.s.i.g. To accomplish this, the gears 18 preferablyhave a radius of 1 inch, a thickness of 1 inch, and each successivelygenerated delivery compartment 18a (13 per gear) is capable ofdelivering 0.045 cubic inch of cryogenic fluid. The passageway 36preferably has a capacity of less than approximately 0.14 cubic inch.Moreover, the gears 23, which are preferably heliquad gears, areselected to have a pumping capacity of 6 gallons per minute. The gears18 and 23 are driven by a motor so that a rotational velocity of 600revolutions per minute is realized.

It should be understood that modifications of various of the structuraland functional features of the illustrated embodiment of the pump wouldbe obvious to those skilled in the art and would not depart from theinvention, various features of which are set forth in the followingclaims.

What is claimed is:

1. A pump for handling cryogenic liquids which comprises a housing thatdefines an intake chamber having an intake port communicating therewith,a pumping chamber having an outlet port communicating therewith, and apassageway providing communication between said chambers; a first rotarypositive displacement pumping means mounted within said intake chamberso that rotary motion imparted thereto results in the successivegeneration of delivery compartments by said first pumping means that areadvanced from said inlet port to the inlet of said passageway; a secondrotary positive displacement pumping means mounted within said pumpingchamber so that rotary motion imparted thereto results in the successivegeneration of pumping compartments by said second pumping means that areadvanced from the outlet Qfsaid passageway to said outlet port; andmeans SYl'lChIOIllZil'lg the rotary motion of said first and secondpumping means so that successive ones of said pumping compartmentstransiently communicate with at least one of said successively generateddelivery compartments through said passageway, each of said pumpingcompartments having a volumetric capacity greater than the Volumetriccapacity of the corresponding delivery compartments transientlycommunicating therewith and said communicating passageway having avolumetric capacity such that some liquid is supplied from thesuccessively generated delivery compartments to said successivelygenerated pumping compartments that transiently communicate therewith.

2. A device for pumping cryogenic liquids from a low pressure portion ofa system to a higher pressure portion of the system, which devicecomprises a housing that defines an intake chamber having an intake portcommunieating therewith and with the liquid supplied from the system, apumping chamber having an outlet port communicating therewith and withthe higher pressure portion of the system, and a passageway providingcommunication etween said chambers; a first pair of positivedisplacement rotary pumping members mounted within said intake chamberso that rotary motion imparted thereto results in the successivegeneration of delivery compartments by said first pair of pumpingmembers that deliver quantities of the liquid from said inlet port tothe inlet of said passageway; a second pair of positive displacementrotary pumping members mounted within said pumping chamber so thatrotary motion imparted thereto results in the successive generation ofpumping compartments by said second pair of pumping members that pumpsuccessive portions of the delivered liquid from the outlet of saidpassageway to said outlet port; and means synchronizing the rotarymotion of said first and second pairs of pumping members so thatsuccessive ones of said pumping compartments transiently communicatewith at least one of said successively generated delivery compartmentsthrough said passageway; each of said pumping compartments having avolumetric capacity greater than the volumetric capacity of thecorresponding delivery compartments transiently communicating therewithand said communicating passageway having a volumetric capacity less thanthe volumetric capacity of the successively generated deliverycompartments that communicate through said passageway with one of saidsuccessively generated pumping compartments.

3. A pump for handling cryogenic liquids which comprises a housing thatdefines an intake chamber having an intake port communicating therewith,a pumping chamber having an outlet port communicating therewith, and apassageway providing communication between said chambers; a first pairof driven mating gear members mounted within said intake chamber so thatrotary motion imparted thereto relative to the intake chamber definingwalls of said housing results in the successive generation of deliverycompartments by the teeth thereof that are advanced from said inlet portto the inlet of said passageway; a second pair of driven mating gearmembers mounted with in said pumping chamber so that rotary motionimparted thereto relative to the pumping chamber defining walls of saidhousing results in the successive generation of pumping compartments bythe teeth thereof that are advanced from the outlet of said passagewayto said outlet port; and means synchronizing the rotary motion of saidfirst and second pairs of driven mating gear members so that successiveones of said pumping compartments transiently communicate with at leastone of said successively generated delivery compartments through saidpassageway, each of said pumping compartments having a volumetriccapacity greater than the volumetric capacity of the correspondingdelivery compartments transiently communicating therewith and saidcommunicating passageway having a volumetric capacity such that someliquid is supplied from the successively generated delivery compartmentsto said successively generated pumping compartments that transientlycommunicate therewith.

4. A device for pumping cryogenic liquids from a low pressure portion ofa system to a higher pressure portion of the system, Which devicecomprises a housing that defines an intake chamber having an intake portcommunicating therewith and with the liquid supplied from the lowpressure portion of the system, a pumping chamber having an outlet portcommunicating therewith and with the higher pressure portion of thesystem, and a passageway providing communication between said chambers;21 first pair of driven mating gear members mounted within said intakechamber in driving contact with each other so that rotary motionimparted to one of said pair results in the other of said pair beingdriven thereby, the teeth of said driven mating gear members effectingthe successive generation of delivery compartments as said gear membersare rotated from said inlet port to the inlet of said passageway andrelative to the intake chamber defining walls of said housing, a pair ofheliquad gear members mounted in close meshing but non-contactingrelationship within said pumping chamber, the teeth of said heliquadgear members eifecting the successive generation of pumping compartmentsas said gears are advanced from the outlet of said passageway to saidoutlet port and relative to the pumping chamber defining walls of saidhousing; and means connecting one of said pair of driven gear members toone of said heliquad gear members and the other of said pair of drivengear members to the other of said heliquad gear members so that rotarymotion is imparted to said heliquad gear members which is synchronizedwith the rotary motion of said driven gear members whereby successiveones of said generated pumping compartments transiently communicate withat least one of said successively generated delivery compartmentsthrough said communicating passageway; each of said pumping compartmentshaving a volumetric capacity greater than the volumetric capacity of thecorresponding delivery compartments transiently communicating therewithand said communicating passageway having a volumetric capacity less thanthe volumetric capacity of the successivel generated deliverycompartments that communicate through said passageway with one of saidsuccessively generated pumping compartments.

No references cited.

1. A PUMP FOR HANDLING CRYOGENIC LIQUIDS WHICH COMPRISES A HOUSING THATDEFINES AN INTAKE CHAMBER HAVING AN INTAKE PORT COMMUNICATING THEREWITH,A PUMPING CHAMBER HAVING AN OUTLET PORT COMMUNICATING THEREWITH, AND APASSAGEWAY PROVIDING COMMUNICATION BETWEEN SAID CHAMBERS; A FIRST ROTARYPOSITIVE DISPLACEMENT PUMPING MEANS MOUNTED WITHIN SAID INTAKE CHAMBERSO THAT ROTARY MOTION IMPARTED THERETO RESULTS IN THE SUCCESSIVEGENERATION OF DELIVERY COMPARTMENTS BY SAID FIRST PUMPING MEANS THAT AREADVANCED FROM SAID INLET PORT TO THE INLET OF SAID PASSAGEWAY; A SECONDROTARY POSITIVE DISPLACEMENT PUMPING MEANS MOUNTED WITHIN SAID PUMPINGCHAMBER SO THAT ROTARY MOTION IMPARTED THERETO RESULTS IN THE SUCCESSIVEGENERATION OF PUMPING COMPARTMENTS BY SAID SECOND PUMPING MEANS THAT AREADVANCED FROM THE OUTLET OF SAID PASSAGEWAY TO SAID OUTLET PORT; ANDMEANS SYNCHRONIZING THE ROTARY MOTION OF SAID FIRST AND SECOND PUMPINGMEANS SO THAT SUCCESSIVE ONES OF SAID PUMPING COMPARTMENTS TRANSIENTLYCOMMUNICATE WITH AT LEAST ONE OF SAID SUCCESSIVELY GENERATED DELIVERYCOMPARTMENTS THROUGH SAID PASSAGEWAY, EACH OF SAID PUMPING COMPARTMENTSHAVING A VOLUMETRIC CAPACITY GREATER THAN THE VOLUMETRIC CAPACITY OF THECORRESPONDING DELIVERY COMPARTMENTS TRANSIENTLY COMMUNICATING THEREWITHAND SAID COMMUNICATING PASSAGEWAY HAVING A VOLUMETRIC CAPACITY SUCH THATSOME LIQUID IS SUPPLIED FROM THE SUCCESSIVELY GENERATED DELIVERYCOMPARTMENTS TO SAID SUCCESSIVELY GENERATED PUMPING COMPARTMENTS THATTRANSIENTLY COMMUNICATE THEREWITH.